The field of the invention pertains to multiple audio loudspeakers to realistically recreate the direct and ambient sound of an audio only, or an audio visual work such as a movie or television program and, in particular, in a home theater setting to provide sound from all directions to the viewer-listener, and more particularly, this invention relates to automatically adjusting the sound delivered to loudspeakers according to the relative location of the loudspeakers and the listener.
Despite the improvements in the overall sound quality provided by sophisticated stereophonic sound systems, many consumers believe contemporary sound systems lack the sense of sonic realism associated with live sound. Sound reproduction systems, while meeting quantitative acoustic performance criteria relative to frequency response, distortion, and dynamic range, can subjectively evoke a wide range of listener perceptions of sonic realism from a qualitative point of view.
Some sound systems achieve an enhanced spatial quality to reproduced sound, while avoiding the introduction of sonic artifacts that would detract from the overall sonic experience. The concept can be yet further extended by spatially distributing a substantial number of point sources for reproducing sound in a listening environment to further increase the perceived spaciousness.
While adding a multiplicity of spatially distributed point sources of sound can increase the perception of spaciousness, it also can produce an exaggerated, overblown spatial presentation that lacks realism. Such unnatural sound reproduction often causes the listener to experience acoustic fatigue. Thus, enhanced spaciousness must balance with the perceived acoustic realism of the resulting sound field in order to completely satisfy the listener.
This balance is particularly important in home theater sound systems where the acoustic requirements for this application differ from those for sound reproduction of stereo music. The key objectives for a home-theater sound system are to establish a convincing surround sound acoustic atmosphere based on ambience and sound effect audio signals captured in the soundtrack; maintain a stereo image panorama of sound in front of the viewer; and reproduce dialog that remains localized to the video screen for any location of the listener.
In essence, satisfactory acoustic performance results when the listener is immersed in a sound field having a three-dimensional spatial quality perceived as authentic in relation to the visual presentation on the video screen. Initial attempts to produce home theater sound included placing a pair of traditional loudspeakers on either side of a centrally located video display.
Such systems improved upon the sound of loudspeakers included within the typical television set. However, the performance of such systems was determined to be unacceptable in the marketplace for at least two reasons. First, listeners located off the center line between the two loudspeakers will not localize dialog to the screen, i.e., perceive the dialog to be solely coming from the screen. Dialog is typically recorded equally in both the left and right channels signals. Localization of dialog will be a point equidistant between the two loudspeakers for a listener on the centerline between the loudspeakers. As a listener moves off the center line, the listener will move closer to one loudspeaker and farther away from the other.
Localization of dialog will shift to the direction from which the first arriving signal originates. This will be the closest loudspeaker. Dialog collapses to the near loudspeaker as a listener moves off axis. The localization of dialog will be displaced from the location of the video image for off axis listeners, and the illusion that the characters on screen are actually speaking for off axis listeners will be destroyed. Second, a pair of stereo loudspeakers located on either side of the visual display confines the sound field to the space in front of the listener, in the plane of the loudspeakers. There is, thus, no sense of immersionxe2x80x94a sense that sound events occur to the side or behind the listener as well as in front of the listener.
Thus, there remains a need for a home theater surround sound loudspeaker system which operates using relatively simple components having mass market appeal at a reasonable cost. Of particular importance in these systems is the desirability that they present a consistent ambient sound field that automatically adjusts for audience location.
The invention provides a system and method for adjusting sound delivery in a home theater.
The system includes a plurality of loudspeakers located in an area. The loudspeakers are coupled to a sound generating source. A camera is oriented to acquire images of the area. An image processing system is coupled to the camera and the sound generating source. Image processing system identifies the positions of the speakers and the position of a listener in the area from the images. The image processing system uses the positional information to automatically adjust the sound to reflect the relative positions of the loudspeakers and the listener.